Wow - so here's a monster of a problem. The greatest kudos the internet can offer to anyone who has a solution. First the build:
3800x cooled by Corsair h100 XT
Asus x570 i gaming
32gs 3600mhz cl16 ram (Trident Z neo)
WD Black 500g nvme
Crucial 1TB nvme
1080ti
Corsair SF750 platinum power supply
All inside an ncase m1. Gpu never went above 65 and cpu never went above 70.
Played on this a fair bit, then it started crashing more and more often. A crash would happen following severe system slowdown for about 5 seconds - the system would freeze, then reboot. Following a crash, the system is unable to post. After shutting down and turning back on a few times by holding down the power switch, the system starts rebooting itself, then it goes into a kind of BIOS safe mode. My first guess was the mobo was dying - despite being about 2 months old. The bios is updated. Anyways, after restarting several times, the system would eventually be able to post and return to windows. It now happens so frequently, the system is basically unusable. Here is what I have tried:
1. Swapped the motherboard for another of the same model.
2. Swapped the ram.
3. No errors on memtest
4. Swapped out the WD Black nvme.
5. Swapped out the video card.
6. Swapped the power supply.
7. Hell, I even swapped the cooler to a D15 because I was running out of things to swap.
8. And at this point, I decided screw it, and swapped the case, too.
I haven't swapped the cpu. I have checked to see that it has been mounted properly. My understanding of failing cpus is that they typically won't even post. I was pretty sure the mobo was faulty or dying, but swapping this did absolutely nothing. My best guess is that there might have been a bunch of these mobos produced with faults? Maybe the 3800x is faulty? Checking windows logs, errors would show that the system wasn't shut down properly, but no indication of a specific device. I have put dozens of hours into trying to figure this thing out, and I'm just completely stumped.